Biology subjects

Penick, C.

Publications and source records attributed to Penick, C..

4 recordsLinked to original sources

bioRxiv2026

Invasive species undermine the bioark hypothesis in a low-latitude urban biodiversity hotspot

Urbanization often reduces local biodiversity, yet cities can maintain surprisingly high total species richness at broader spatial scales. This paradox has led to the "cities-as-bioarks" hypothesis, which proposes that protected remnant habitats within cities can function as refuges for native species. However, most evidence supporting this hypothesis comes from higher latitudes, and it remains unclear whether remnant habitats in low-latitude cities can serve the same role. We surveyed ant communities across 60 sites in Atlanta, Georgia (USA), spanning streetscapes, manicured parks, and forested parks, to test whether relatively undisturbed urban forests support the highest native diversity. Contrary to the bioark prediction, native species richness was lowest in forested parks and highest in habitats with intermediate disturbance. Community composition varied with habitat structure, but surface temperature was not a significant predictor of richness or composition. Instead, native abundance and richness declined strongly with increasing abundance of the invasive Asian needle ant, Brachyponera chinensis, a forest-adapted invader capable of dominating relatively intact habitats. In contrast, two other invasive species, the red imported fire ant Solenopsis invicta and the Argentine ant Linepithema humile, were largely restricted to more disturbed habitats and had comparatively weaker associations with native diversity loss. These findings refine the bioark hypothesis by demonstrating that habitat protection alone may be insufficient to conserve insect diversity in warmer regions, and instead must be paired with active invasive species management.

ecology↗

bioRxiv2026

A Functional Basis for the Developmental Sequence of the Macrostructure of the Venus Flower Basket (Euplectella aspergillum)

Despite receiving significant interest from the biological and engineering communities, several questions about the underlying reasons for the form of the deep-sea sponge Venus Flower Basket (Euplectela aspergillum) remain unanswered. In particular, the basis for the sequence of emergence of three distinct macroscopic geometric features, while speculated upon, has not been validated. These features are (i) an interwoven cross-grid in the juvenile stage, (ii) a diagonal weave atop this initial grid, and (iii) a helical ridge that emerges in the mature phase of the sponge. This work uses computational design and additive manufacturing to fabricate models of each of these phases in sequence and subjects the models to mechanical tests in compression, bending and torsion. The results show that each feature has a singular advantage, even after accounting for the increase in mass associated with their addition: increased compliance for interwoven cross-grid, increased bending stiffness for diagonal weaves, and improved torsional rigidity for the helical ridge. The work postulates that the prioritization of compliance in the juvenile phase and a transition to a stiffer structure in the mature phase is a strategy that enables the sponge to avoid high internal stresses to avoid failure in its inherently brittle, silica-derived architecture. Highlights1. The benefits of three macrostructural design elements of the Venus Flower Basket (E. aspergillum) that emerge sequentially in its development are examined: (i) the interweaving cross-grid, (ii) the diagonal weave that overlays this cross-grid, and (iii) the helical ridge reinforcement that forms over this diagonal weave. 2. For the first time, this work models each of these design features sequentially and studies their mechanical benefits through an experimental exploration of the behavior of idealized geometries in three test domains: compression, bending, and torsion. 3. Results show that each of these three structural elements has a unique functional advantage depending on the organisms growth stage, even after accounting for differences in mass: interweaving enables higher compliance under compression, the diagonal weave improves bending stiffness, and the helical ridge improves torsional stiffness.

developmental biology↗

bioRxiv2025

Dual strategies in ant social immunity: Chemical diversity and pathogen specificity in antimicrobial defense

The evolution of sociality provides many benefits but also increases the risk of disease transmission. In response, social insects have evolved social immune defenses, which includes the production and communal use of antimicrobial compounds. The origins of sociality in insects are closely associated with the development of exocrine glands that secrete these antimicrobials. However, it is unclear how social insects prevent pathogens from evolving resistance to these compounds given their frequent use. We tested whether ants reduce this risk by producing chemically diverse and pathogen-specific antimicrobial compounds. Using solvents of varying polarity, we extracted antimicrobial compounds from six ant species and tested their inhibitory effects on Gram-positive bacteria, Gram-negative bacteria, and a fungal pathogen. Our results show that ants produce multiple classes of antimicrobial compounds with distinct chemical properties and targeted activity, though the strength and specificity of inhibition vary across species. Notably, five of the six ant species tested inhibited Candida auris, an emerging fungal pathogen of critical concern in human medicine due to its multidrug resistance. These findings suggest that social immunity in ants is reinforced by both chemical diversity and pathogen specificity, offering an evolutionary strategy that may help prevent antimicrobial resistance in dense, socially complex environments.

ecology↗

bioRxiv2018

Expanded view of the ecological genomics of ant responses to climate change

Given the abundance, broad distribution, and diversity of roles that ants play in many ecosystems, they are an ideal group to serve as ecosystem indicators of climatic change. At present, only a few whole-genome sequences of ants are available (19 of > 16,000 species), mostly from tropical and sub-tropical species. To address this limited sampling, we sequenced genomes of temperate-latitude species from the genus Aphaenogaster, a genus with important seed dispersers. In total, we sampled seven colonies of six species: A. ashmeadi, A. floridana, A. fulva, A. miamiana, A. picea, and A. rudis. The geographic ranges of these species collectively span eastern North America from southern Florida to southern Canada, which encompasses a latitudinal gradient in which many climatic variables are changing rapidly. For the six genomes, we assembled an average of 271,039 contigs into 47,337 scaffolds. The mean genome size was 370.5 Mb, ranging from 310.3 to 429.7, which is comparable to that of other sequenced ant genomes (212.8 to 396.0 Mb) and flow cytometry estimates (210.7 to 690.4 Mb). In an analysis of currently sequenced ant genomes and the new Aphaenogaster sequences, we found that after controlling for both spatial autocorrelation and phylogenetics ant genome size was marginally correlated with sample site climate similarity. Of all examined climate variables, minimum temperature showed the strongest correlation with genome size, with ants from locations with colder minimum temperatures having larger genomes. These results suggest that temperature extremes could be a selective force acting on ant genomes and point to the need for more extensive sequencing of ant genomes.

genomics↗